Radiography is a nondestructive
analysis technique used to examine the interior
details of the package. It operates on the principle of
transmission of X-Rays through different materials.
The ability of a material to block X-Rays increases with its
density. It is this dissimilar transmission of X-rays through different
materials that is utilized to create an image of various contrasts.
X-Ray imaging may be accomplished on film, by fluoroscopy, or by
using image intensifying video systems.
typical modern X-Ray inspection equipment has a filament that produces an
electron beam used to
excite a target into producing
X-Rays. The X-Ray
emissions are then directed to and transmitted through the specimen. The
X-Rays are collected by a detector, translated into electric
signals, amplified, and transformed into an X-Ray image.
varying densities of the various materials comprising the specimen allow
different amounts of X-Rays to pass through, resulting in varying
grayscale levels on the
The quality of the X-Ray image formed therefore depends not only
on the proper operation of the X-Ray equipment used, but on the
composition of the specimen as well. Some materials used in
semiconductor assembly, such as aluminum wires, are transparent to X-Ray,
and are therefore invisible in X-Ray images.
Example of a Top View X-ray Photo of an IC
radiography is commonly used to inspect for
wiresweeping and other
wirebond problems, die attach voids, package voids and cracks. It is
excellent for determining leadframe outlines as well. Traditional x-ray
systems use photosensitive films to record the x-ray image. Since X-Rays
are not easy to focus, this method produces low-resolution images, which
greatly limits its usefulness.
Example of an X-ray Inspection System
Today, X-Ray systems use a
source, real-time detection and automated manipulation of the sample to
achieve higher resolution and throughput. These systems are capable of
detecting much finer package details and defects.
Microscopy; FA Lab
Equipment; Basic FA
Package Failures; Die
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